1. Field of Invention
The present invention relates generally to the field of oilfield exploration, production, and testing), and more specifically to protection of polymeric components used in such ventures.
2. Related Art
Electrical submersible pumps (ESPs) are used for artificial lifting of fluid from a well or reservoir. An ESP typically comprises an electrical submersible motor, a seal section (sometimes referred to in the art as a protector) which functions to equalize the pressure between the inside of the system and the outside of the system and also acts as a reservoir for compensating the internal oil expansion from the motor; and a pump having one or more pump stages inside a housing. The protector may be formed of metal, as in a bellows device, or an elastomer, in which case the protector is sometimes referred to as a protector bag. Elastomers may also be used in packer elements, blow out preventer elements, O-rings, gaskets, electrical insulators and pressure sealing elements for fluids.
Common to all of these uses of elastomers is exposure to hostile chemical and mechanical subterranean environments that tend to unacceptably decrease the life and reliability of the elastomers.
Three basic approaches have been taken in addressing the pump protector problem. Replacing the elastomer with a thin metal membrane or bellows may be an expensive alternative that requires extensive redesign of the parts together with their mechanical attachment and interfaces. Improving the bulk properties of the elastomer material using additives is another alternative; however, that may require conflicting compromises in the mechanical, chemical, or reliability performance of the finished part. Typically, it is not feasible to find a combination of additives that satisfy all the requirements, or it is prohibitively expensive to either procure the additive materials or to manufacture the part. Applying some type of protective coating to elastomer seals has been tried in the medical, computer and electronics, defense, automotive, food processing and aerospace industries. Focus has been on various types and methods of applying either a metal or a polymer coating to protect elastomeric seals for either low friction, abrasion resistance or for chemically enhancing the wear resistance and environmental resistance of the part without changing the physical properties of the base elastomer. For example, U.S. Pat. No. 5,075,174 discusses Parylene-coated silicone elastomeric gaskets for use in the computer and electronics industry. There are two principal coating methods: Physical Vapor Deposition (PVD) and Chemical Vapor Decomposition (CVD). PVD coatings are typically made either by thermal evaporation or sputtering. Unfortunately, PVD is a line-of-sight coating process; therefore, coverage of the substrate is poor when a part is odd shaped or has cavities. In contrast, CVD is not restricted to line-of-sight; therefore it can coat all surfaces of the substrate. Examples of film coatings on elastomers include a silane polymer that was applied by plasma deposition in a radio frequency/microwave dual power source reactor (see U.S. Pat. No. 6,488,992), and a blend of elastomer and polyethylene co-extruded onto rubber weather stripping material (U.S. Pat. No. 5,110,685).
There remains a need in the natural resources exploration and production field for improving reliability and life of elastomeric and other polymeric components used in oilfield environments, such as protector bags, packer elements, pressure seals, valves, blow out preventer components, and the like.